From European Patent Disclosure EP 0 520 540 A1, a heddle frame is known, having two frame rods, disposed horizontally at a spacing from one another, which are joined on their respective ends by a respective vertical lateral sampson. The lateral sampsons and the frame rods thus form a rectangular frame, called a heddle frame. Support rails on which heddles are seated are retained on the frame rods. Each heddle has an eyelet through which a warp yarn extends. Moving the entire heddle frame up and down opens or closes sheds into which weft yarns are to be inserted. Drive bars that extend all the way through the lateral sampsons serve to move the heddle frame. To that end, each lateral sampson is provided with a hollow chamber, which is accessible at its lower end through a threaded opening and at its upper end through a through bore. The drive rod is provided with threads on its upper and lower ends. It extends through the hollow chamber of the lateral sampson, and its male thread meshes with the thread of the threaded bore of the lateral sampson. Its other end extends through the through bore, where it is locked or clamped by means of a nut that is braced on the surface of the lateral sampson that surrounds the through bore.
The drive rod is provided on its lower end with a coupling device, which is in engagement with the drive mechanism. For changing the heddle frame, the drive rods are uncoupled, so that the heddle frame can be removed along with the drive rods from the power loom. The accessibility of the coupling devices is limited.
From European Patent Disclosure EP 0 467 808 A1, a connecting system between drive rods and heddle frames is known, in which the heddle frame is connected at its upper end to the drive rod or to a drive cable. Serving as the connecting device is a hook whose jaw is in positive engagement with a corresponding profile of the drive rod, and whose other end is connected to the lateral sampson. The drive rod or the drive cable extends through a groovelike channel in the lateral Sampson.
In all the arrangements described above, and particularly the last one, limited buckling of the drive rod can occur. The buckling occurs especially under load, because of the strong compressive forces acting on the drive rods. These forces can damage the groove or bore through which they extend. Such damage consequently rapidly causes failure of the lateral sampsons, which break. The damage reduces the already low fatigue strength of the lateral sampsons, which typically are of aluminum.
With this as the point of the departure, it is the object of the invention to create an improved heddle frame whose lateral sampsons have a longer service life.